1. Field of the Invention
The present invention relates to an electrode for an electrochemical capacitor which comprises an inherently conductive polymer, and to a process for the production thereof. The invention also relates to an electrochemical capacitor which comprises such an electrode.
2. Discussion of Background Information
Electrochemical capacitors (sometimes also referred to as “supercapacitors”) are devices which comprise two electrodes which are separated by a liquid or solid electrolyte. Electrical energy is stored at the electrode/electrolyte interface. This type of energy storage has recently attracted increased attention due to the application of new materials which allow high charge densities, i.e., high surface area activated carbons, metal oxides and electrically conducting polymers, and the potential for increased capacitance associated therewith.
Although the overall structure of an electrochemical capacitor is similar to that of an electrochemical battery, there are significant differences between these two types of energy storage devices. For example, in the electrochemical capacitor, energy storage is by means of static charge rather than by an electrochemical process that is inherent to the battery. Moreover, whereas the electrochemical battery delivers a fairly steady voltage in the usable energy spectrum, the voltage of the electrochemical capacitor is linear and drops evenly from full voltage to zero volts. Accordingly, rather than operating as a main battery, electrochemical capacitors are more commonly used as memory backup to bridge short power interruptions. Another application is improving the current handling of a battery. The electrochemical capacitor is placed in parallel to the battery terminal and provides current boost on high load demands. The electrochemical capacitor may also find use in portable fuel cells to enhance peak-load performance. The main advantages of electrochemical capacitors in comparison with batteries are a much higher power density (i.e., short charge and discharge times) and thermal stability (usually from −5° C. to 85° C.), as well as an excellent cycle life (usually more than 100,000 cycles). New materials of high charge density will foster the miniaturization of electrochemical capacitors and, therefore, make them more suitable for use in portable electrical devices such as, e.g., notebook PCs and cellular phones. Examples of potential fields of application of electrochemical capacitors, in addition to their use as memory backup in computers, telecommunications and consumer electronics, are electric vehicles (capacitor-battery hybrid), automotive subsystems (catalyst preheating, cold-start assistance), industrial (factory automation, robotics), and military applications (electric subsystems, “silent” vehicles).